1. Technical Field
The present invention relates to an image display device, an imaging apparatus mounted with the image display device as a finder device, and an image display method.
2. Related Art
For example, for a beginner who walks in mountains and sees Yatsugatake Peaks through binoculars, it is difficult to know which mountain is Akadake and what mountain is seen by the side thereof. Here, when each of optical images of mountains seen within the binoculars is synthesized with a mountain name to be displayed, usability of the binoculars is improved.
Or, in constructing a building in a vacant lot of a city, when a construction designer can observe a state where a CG image of a designed building stands up in the vacant lot together with an optical image of a surrounding building group by observing a group of buildings around the vacant lot through a finder device of a digital camera owned by himself, a landscape after the construction may be checked in advance. This provides convenience.
If a technology that when a person, who wants to go to a destination but gets lost, sees a corresponding direction through a finder of a digital camera, the location of the destination hidden by a building group or names of surrounding buildings are displayed within the finder, is achieved, the usefulness of the digital camera is improved.
There has already been a technology that when a lens of a digital camera is directed to a specific direction, and a capture image (a live view image) is displayed on an LCD display device at the rear surface of the camera, for example, information or a place name of a landmark, or a building name is displayed to be superimposed on a capture image (e.g., Patent Literature 1 (JP-A-2006-59136)).
When a main object is to know the landmark information or the building name, a live view image of a subject may be displayed on the LCD display device provided on, for example, the rear surface of the camera, and, for example, the building name may be displayed to be superimposed on the live view image. However, when a main object is to observe a subject, what is highly demanded is to directly see a clear optical image of the subject through binoculars or an observation window of an optical finder device.
Patent Literature 2 (JP-A-2011-253512) as described below discloses a device which displays electronic information, such as illustrated information, to be synthesized together with the field of view seen through an observation window when a subject is observed through, for example, binoculars or a magnifying glass.
When an optical image of the subject is directly observed with an eye, and, for example, a name of a landmark, as the electronic information, is displayed to be synthesized with the field of view, it is possible to observe a clear optical image and also to know required electronic information together with the image. However, Patent Literature 2 does not disclose how to specifically configure the device of realizing the technology.
A technology of displaying electronic information to be superimposed on an optical image may be realized by applying a conventional technology disclosed in, for example, Patent Literature 3 (JP-A-2010-107529) as described below. A digital camera disclosed in Patent Literature 3 is configured such that when a displayed image of a projection-type display device provided within an optical finder is projected to be superimposed on an optical image of a subject visible to an eye of a user through the optical finder. Accordingly, when required electronic information is displayed on the projection-type display device, the user becomes capable of seeing an image in which the electronic information is superimposed on the optical image, with his/her eye.
It is easy to display an optical image of a subject and relevant information thereof, such as names, at roughly matching positions around the optical image. However, for example, when a mountain range including a series of many mountains are seen through binoculars, wrong information may be provided to a user when each mounting name is displayed to be superimposed on a slightly shifted position. Accordingly, it is required to display electronic information at matching positions on an optical image of a subject with a high precision.
For example, Patent Literature 4 (JP-A-2009-200552) and Patent Literature 5 (JP-A-H03-292067) disclose a finder device in which an optical finder and an electronic viewfinder are combined with each other. A capture image of a subject displayed on the electronic viewfinder of the finder device is not an optical image of the subject which comes into the optical finder. The capture image is an optical image which is photographed by an imaging device through light-condensing at a photographing lens provided at a location slightly apart from the finder device.
That is, a parallax occurs between the optical image which has passed through the optical finder, and the capture image displayed on the electronic viewfinder. In a case of a single focal lens camera, the parallax may be easily corrected, because there is always a fixed relationship. However, when the photographing lens is a zoom lens, the parallax may be varied according to a magnification change. Thus, it becomes difficult to perform alignment of the optical image with the capture image with a high precision.